High-pressure tank, high-pressure tank mounting apparatus and method for manufacturing high-pressure tank

ABSTRACT

A high-pressure tank comprises a liner, a strengthening layer including a first helical layer and a first hoop layer each including a carbon fiber, and a protective layer including a second helical layer and a second hoop layer each including a glass fiber, in this order. The high-pressure tank is provided with a stress-generating portion, a reinforcement layer includes a first area α overlapping the stress-generating portion in a stacking direction and a second area β that is an area except for the first area, and a one-round portion including a final crossing portion at an end of winding of the glass fiber constituting the second hoop layer overlaps the second area in the stacking direction.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a division of U.S. patent application Ser.No. 16/432,019, filed Jun. 5, 2019, which claims priority to JapanesePatent Application No. 2018-117678, filed on Jun. 21, 2018, the contentsof which are incorporated herein by reference in their entirety.

BACKGROUND Field

The present disclosure relates to a high-pressure tank, a high-pressuretank mounting apparatus and a method for manufacturing the high-pressuretank.

Related Art

There is a known configuration of a tank for storing and sealinghigh-pressure fluid that includes a liner forming a space for storingthe fluid and a reinforcement layer disposed to cover the liner andincluding fiber-reinforced plastic (FRP). Specifically, for example,there is a known configuration in which a layer including a carbon fiberreinforced plastic, i.e., CFRP, (CFRP layer) is formed on the liner asthe reinforcement layer and a protective layer (GFRP layer) including aglass fiber reinforced plastic, i.e., GFRP, is formed on the CFRP layer.See, for example, Patent Literature 1.

Patent Literature 1: JP 2013-224856A

Inventors of this application have discovered that repetition of anincrease and decrease cycle of an inner pressure for such ahigh-pressure tank sometimes causes a crack in a surface of theprotective layer. Therefore, technology to reduce the crack in thesurface of the reinforcement layer is desired.

SUMMARY

According to one aspect of the present disclosure, a high-pressure tankis provided. The high-pressure tank comprises a liner including acylindrical portion and hemispherical dome portions on both sides of thecylindrical portion, and a reinforcement layer covering an outer surfaceof the liner. The reinforcement layer includes a strengthening layerthat is formed on the liner and includes a first helical layer includinga carbon fiber in helical winding and a first resin, and a first hooplayer including the carbon fiber in hoop winding and the first resin.The reinforcement layer includes a protective layer that is formed onthe strengthening layer and includes a second helical layer including aglass fiber in the helical winding and a second resin, and a second hooplayer formed on the second helical layer and including the glass fiberin hoop winding and the second resin. The high-pressure tank furthercomprises a stress-generating portion generating a local stress in thereinforcement layer. The stress-generating portion is at least one of(a) a convex portion locally forming a convex shape on the outer surfaceof the liner, (b) a step portion where the carbon fiber or the glassfiber crosses itself at a transition part where a winding angle of thecarbon fiber or the glass fiber changes in the reinforcement layer, (c)a fiber joining portion where ends of the carbon fibers, ends of theglass fibers, or ends of the carbon fiber and the glass fiber are joinedtogether in the reinforcement layer, (d) an end crossing portion wherethe carbon fiber entwines and crosses the same carbon fiber or the glassfiber entwines and crosses the same glass fiber on at least one of awinding start of the carbon fiber, a winding end of the carbon fiber,and a winding start of the glass fiber, (e) a helical crossing portionwhere the carbon fiber cross itself in the first helical layer disposedin contact with the liner. The reinforcement layer includes a first areathat overlaps the stress-generating portion in a stacking direction ofthe strengthening layer and the protective layer stacked one on theother and a second area that is an area except for the first area.One-round portion including a final crossing portion where the glassfiber entwines and crosses the same glass fiber at an end of winding ofthe glass fiber in the second hoop layer overlaps the second area in thestacking direction.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view of a high-pressure tank.

FIG. 2 is a partially enlarged schematic cross-sectional view of anouter wall of the high-pressure tank.

FIG. 3 is a flowchart illustrating an outline of a method formanufacturing the high-pressure tank.

FIG. 4 is an explanatory diagram schematically illustrating aconfiguration of a final crossing portion.

FIG. 5 is an explanatory diagram illustrating a schematic configurationof a filament winding apparatus.

FIG. 6A is an explanatory diagram illustrating a process in which acrack is caused in a second hoop layer.

FIG. 6B is an explanatory diagram illustrating the process in which thecrack is caused in the second hoop layer.

FIG. 6C is an explanatory diagram illustrating the process in which thecrack is caused in the second hoop layer.

FIG. 7 is a schematic cross-sectional view of an example of a positionalrelation between a terminal portion and a stress-generating portion.

FIG. 8 is an explanatory diagram illustrating an example of a convexportion formed on an outer surface of a liner.

FIG. 9 is an explanatory diagram illustrating another example of thestress-generating portion.

FIG. 10 is an explanatory diagram illustrating another example of thestress-generating portion.

FIG. 11 is an explanatory diagram illustrating another example of thestress-generating portion.

FIG. 12 is an explanatory diagram illustrating another example of thestress-generating portion.

FIG. 13 is a perspective view of the high-pressure tank installed in ahigh-pressure tank mounting apparatus.

DETAILED DESCRIPTION A. First Embodiment

(A-1) Overall Configuration of High-Pressure Tank:

FIG. 1 is a schematic cross-sectional view of a high-pressure tank 100in a first embodiment of the present disclosure. The high-pressure tank100 stores high-pressure fluid. In the present embodiment, thehigh-pressure tank 100 stores compressed hydrogen as the fluid and is,for example, installed in a hydrogen tank mounting apparatus such as afuel cell vehicle. The high-pressure tank 100 includes a liner 10, areinforcement layer 70, and mouthpieces 21 and 22. FIG. 1 and each ofthe figures described later schematically illustrates states ofcomponents of the high-pressure tank 100 according to the presentdisclosure, and thus a size of each of the components shown in thefigures does not represent a specific size.

The liner 10 includes a space for sealing the fluid in it. The liner 10includes a cylindrical portion 16 that is formed in a cylindrical shapeextending in an axis O direction of the high-pressure tank 100 and twodome portions 17 and 18 in a substantially hemispherical shape,continuing to both ends of the cylindrical portion 16. The liner 10 maybe formed of, for example, a synthetic resin such as a nylon-based resin(polyamide-based resin) and a polyethylene-based resin or a metal suchas an aluminum alloy. The liner 10 in the present embodiment is formedof nylon. The mouthpieces 21 and 22 are disposed on both ends of theliner 10 at the tops of the dome portions. The mouthpieces 21 and 22 arejoined to the liner 10 by insert molding, for example.

In the present embodiment, the liner 10 includes a plurality ofcomponents jointed together. Specifically, the liner 10 includes linercomponents 11, 12 and 13, and these liner components are disposed in theaxis O direction in this order. The liner component 11 and the linercomponent 12, and the liner component 12 and the liner component 13 canbe joined together by, for example, infrared welding, laser welding, hotplate welding, vibration welding, ultrasonic welding, or the like. Theliner 10 may include a plurality of components other than threecomponents, and may be formed by a different method from joining theplurality of components.

The reinforcement layer 70 is formed to cover an outer surface of theliner 10 so as to reinforce the liner 10 and enhance strength of thehigh-pressure tank 100, i.e., strength against internal pressure of thetank. The reinforcement layer 70 includes, as its constituent materials,a fiber wound around the outer surface of the liner 10 and a resinimpregnated into the fiber.

FIG. 2 is a partially enlarged schematic cross-sectional view of anouter wall of the high-pressure tank 100. The reinforcement layer 70includes a carbon fiber reinforced plastic layer 74 (hereinafter alsoreferred to as a CFRP layer 74) including the carbon fiber reinforcedplastic (CFRP) and disposed on the liner 10, and a glass fiberreinforced plastic layer 72 (hereinafter also referred to as a GFRPlayer 72) including the glass fiber reinforced plastic (GFRP) anddisposed on the CFRP layer. The CFRP layer 74 is also referred to as astrengthening layer. The GFRP layer 72 is also referred to as aprotective layer.

The CFRP layer 74, i.e., strengthening layer, includes a layer in whicha carbon fiber is wound around by hoop winding (referred to as a firsthoop layer 73) and a layer in which a carbon fiber is wound around byhelical winding (referred to as a first helical layer 71). See FIG. 7described later. The “hoop winding” is a way of winding in which awinding angle of a fiber relative to the axis O direction issubstantially right angle while the “helical winding” is a way ofwinding in which a winding angle of a fiber relative to the axis Odirection is lower than the winding angle of the hoop winding. The“helical winding” is divided into a “high-angle helical winding” and a“low-angle helical winding”. In the high-angle helical winding, thefiber is wound around the axis O at least once, and then a windingdirection of the fiber is turned on any one of the dome portions so asto form a relatively high winding angle. In the low-angle helicalwinding, the winding direction of the fiber is turned on any one of thedome portions before the fiber is completely wound around the axis O soas to form a relatively low winding angle. In the first helical layer71, a layer in which the carbon fiber is wound around by high-anglehelical winding is referred to as a high-angle helical layer 71 a whilea layer in which the carbon fiber is wound around by low-angle helicalwinding is referred to as a low-angle helical layer 71 b.

The winding angle of the fiber relative to the axis O direction may be80° or higher and 90° or lower in the first hoop layer 73, and 70° orhigher and 85° or lower in the high-angle helical layer 71 a, forexample. However, the winding angle of the first hoop layer 73 is higherthan that of the high-angle helical layer 71 a. The winding angle of thefiber relative to the axis O direction in the low-angle helical layer 71b may be 0° or higher and 40° or lower. Preferably, the winding angle inthe low-angle helical layer 71 b is 5° or higher and 35° or lower.

The CFRP layer 74 includes one or more layers respectively of the firsthoop layer 73, the high-angle helical layer 71 a, and the low-anglehelical layer 71 b, and respective layers are stacked in a predeterminedorder. FIG. 2 shows the CFRP layer 74 in which the low-angle helicallayer 71 b, the high-angle helical layer 71 a, the first hoop layer 73,another low-angle helical layer 71 b, another high-angle helical layer71 a, and another first hoop layer 73 are stacked in this order on theliner 10. The stacking order shown in FIG. 2 is an example, and thus thenumber and the stacking order of respective layers constituting the CFRPlayer 74 may vary. The winding angle may be constant in each of thefirst hoop layer 73, the high-angle helical layer 71 a, and thelow-angle helical layer 71 b. However, if a plurality of first hooplayers 73, high-angle helical layers 71 a, or low-angle helical layers71 b are disposed, the winding angles in different layers of the samekind may be different.

The CFRP layer 74 includes a transition part where the winding angle ofthe fiber is changed between the layers. Specifically, for example, thetransition parts where the winding angles are drastically changed existbetween the low-angle helical layer 71 b and the first hoop layer 73 andbetween the low-angle helical layer 71 b and the high-angle helicallayer 71 a. Accordingly, the transition part where the low-angle helicallayer 71 b changes to a layer having a higher winding angle than that ofthe low-angle helical layer 71 b is referred to as a first transitionpart. As described above, in the transition part where the winding angleof the fiber is changed, the fiber is wound around while the windingangle is variously changed, and at the same time, a winding position ofthe fiber is moved to a winding start position of the next layer. Thefirst transition part will be described later in detail.

The GFRP layer 72, i.e., protective layer, includes a second helicallayer 78 which is formed on the CFRP layer 74 and in which a glass fiberis wound around by helical winding, and a second hoop layer 76 which isformed on the second helical layer 78 and in which the glass fiber iswound around by hoop winding. The winding angle in the second helicallayer 78 may be the same as that of the low-angle helical layer 71 b,for example. The winding angle in the second hoop layer 76 may be thesame as that of the first hoop layer 73, for example. There is atransition part where the winding angle is drastically changed betweenthe second helical layer 78 and the second hoop layer 76, like thetransition part in the CFRP layer 74. This transition part is alsoreferred to as a second transition part. The second transition part willbe described later in detail. In the present embodiment, the second hooplayer 76 constitutes an outer surface of the high-pressure tank 100.However, at least part of a surface of the second hoop layer 76 may becovered with some sort of layer. For example, a layer including adifferent kind of resin from the one included in the GFRP layer 72 maybe formed on the at least part of the surface of the second hoop layer76.

As the resin included in each of the layers constituting the CFRP layer74 and the GFRP layer 72, for example, a thermosetting resin such as anepoxy resin or a thermoplastic resin such as a polyester resin and apolyamide resin may be used. The resin included in the CFRP layer 74 isreferred to as a first resin, and the resin included in the GFRP layer72 is referred to as a second resin. In the present embodiment, an epoxyresin is used as the first and second resins. The first and secondresins may be of the same kind or different kinds. If the first andsecond resins are of the same kind, resin properties may bedifferentiated by including or excluding a curing accelerator and areinforcing agent. In addition, if the curing accelerator and thereinforcing agent are included, the resin properties may bedifferentiated by varying kinds and amounts of the curing acceleratorand the reinforcing agent.

(A-2) Method for Manufacturing High-Pressure Tank:

FIG. 3 is a flowchart illustrating an outline of a method formanufacturing the high-pressure tank 100. In order to produce thehigh-pressure tank 100, first of all, the liner 10 is prepared (stepS100). Then, the CFRP layer 74 is formed with a resin-impregnated carbonfiber on the prepared liner 10 (step S110). Subsequently, the secondhelical layer 78 is formed with a resin-impregnated glass fiber on theCFRP layer 74 (step S120), and the second hoop layer 76 is formed withthe resin-impregnated glass fiber on the second helical layer 78 (stepS130). After forming the second hoop layer 76, a final crossing portiondisposed at the end of the winding of the resin-impregnated glass fiberis secured on a surface of the GFRP layer 72 (step S140). The finalcrossing portion will be described later. Then, the resins constitutingthe CFRP layer 74 and the GFRP layer 72 are cured (step S150) so as tocomplete the high-pressure tank 100. The resins can be cured by, forexample, heating using a heating furnace or induction heating using aninduction heating coil that induces high-frequency induction heating.

FIG. 4 is an explanatory diagram schematically illustrating aconfiguration of the final crossing portion 82. The final crossingportion 82 is a portion where the resin-impregnated glass fiber 700 aentwines and crosses the same resin-impregnated glass fiber 700 a at theend of the winding of the resin-impregnated glass fiber constituting thesecond hoop layer 76. The final crossing portion 82 can be formed, forexample, by winding around the resin-impregnated glass fiber 700 a oncealong a circumferential direction of the liner 10 and then entwining itwith the same glass fiber 700 a so as to cross it. Alternatively, thefinal crossing portion 82 may be formed by entwining the glass fiber 700a with the same glass fiber 700 a so as to cross it at a differentportion from where the glass fiber 700 a is wound around once along thecircumferential direction. Securing of the final crossing portion 82 onthe surface of the GFRP layer 72 can be implemented by curing the resinincluded in the final crossing portion 82 on the surface of the GFRPlayer 72. The securing of the final crossing portion 82 may be performedat the same time as the whole reinforcement layer 70 is cured, or priorto it.

FIG. 5 is an explanatory diagram illustrating a schematic configurationof a filament winding apparatus 200 in the present embodiment. Theapparatus is also referred to as an “FW apparatus” hereinafter. The CFRPlayer 74 and the GFRP layer 72 are formed by a filament winding methodusing the same kind of FW apparatus 200. The filament winding method isa method including winding a fiber impregnated with a thermosettingresin around a mandrel, i.e., the liner 10 in the present embodiment,and heating the thermosetting resin to cure it.

The FW apparatus 200 includes a fiber unwinding unit 20, a fiber bundleguiding unit 30, a winding unit 40, and a controller 600. In FIG. 5 , aworkpiece of the FW apparatus 200, that is, the liner 10 provided withthe mouthpieces 21 and 22, or an unfinished tank in which a fiber ispartially wound around the liner 10, is referred to as a work 60.

The fiber unwinding unit 20 has a function to wind off a fiber bundle700 and includes a plurality of bobbins 201 to 204, a plurality ofconveyance rollers 211 to 217, a bundling roller 220, a tension roller230, and an active dancer roller 240.

Each of the plurality of bobbins 201 to 204 is cylindrical, and a towprepreg 710 is wound around it. The tow prepreg 710 is a fiber includingabout 20,000 to 50,000 filaments and impregnated with the resindescribed above. The tow prepreg 710 is the resin-impregnated carbonfiber when the CFRP layer 74 is formed, and the resin-impregnated glassfiber when the GFRP layer 72 is formed. In the following description,the tow prepreg forming the CFRP layer 74 may be simply referred to asthe carbon fiber, and the tow prepreg forming the GFRP layer 72 may besimply referred to as the glass fiber. Some of the plurality ofconveyance rollers 211 to 214 are disposed to correspond to theplurality of bobbins 201 to 204, respectively, and convey the towprepregs 710 that are wound off from the plurality of bobbins 201 to 204to the bundling roller 220. The bundling roller 220 aligns the towprepregs 710 wound off from the plurality of bobbins 201 to 204 so as tomake them into the fiber bundle 700 and wind it off to the tensionroller 230. The tension roller 230 includes a cylinder 231 set at apredetermined pressure to apply a tensile force to the fiber bundle 700.The active dancer roller 240 moves a roller 241 so as to adjust thetensile force of the fiber bundle 700. The tensile force when the fiberbundle 700 is wound around the work 60 can be changed by the pressureset to the cylinder 231. The fiber bundle 700 with the adjusted tensileforce is conveyed to the fiber bundle guiding unit 30 via the rest ofthe plurality of conveyance rollers 215 to 217.

The fiber bundle guiding unit 30 aligns the fiber bundle 700 and guidesit to the work 60. The fiber bundle guiding unit 30 can move along alongitudinal direction of the work 60 as indicated by an outlined arrowso as to change its relative position to the work 60. By changing therelative position of the fiber bundle guiding unit 30 to the work 60, awinding angle of the fiber bundle 700 when the fiber bundle 700 is woundaround the work 60 can be adjusted.

The fiber bundle guiding unit 30 includes an alignment opening 300 and afiber feed section 320. The alignment opening 300 gathers the fiberbundle 700 and align it in a width direction, i.e., a front-to-backdirection of the figure. The fiber feed section 320 includes a firstconvergence roller 330, a second convergence roller 340, and a thirdconvergence roller 350, and uses these three convergence rollers 330,340 and 350 to convey the fiber bundle 700 to the work 60. In thepresent embodiment, the fiber bundle 700 is guided to the work 60 suchthat it enters from a side of the first convergence roller 330 and comesinto contact with an upper circumference of the first convergence roller330, a lower circumference of the second convergence roller 340, and anupper circumference of the third convergence roller 350. The fiberbundle 700 coming out of the fiber bundle guiding unit 30 becomes a beltshape of approximately 5 to 20 mm in width and 0.2 to 0.8 mm inthickness, for example.

The winding unit 40 rotates the work 60 so as to wind the fiber bundle700 around the work 60. The winding unit 40 includes a rotation device400, a rotary shaft 410, and a support shaft 420. The work 60 isinstalled in the winding unit 40 such that the rotary shaft 410 and thesupport shaft 420 overlap the axis O. One end of the rotary shaft 410 issecured to the rotation device 400 while the other end is secured to themouthpiece 21 of the work 60. One end of the support shaft 420 supportsthe work 60 via the mouthpiece 22 in a rotatable manner. When therotation device 400 is actuated, the rotary shaft 410 starts rotating soas to rotate the work 60, whereby the fiber bundle 700 is wound aroundthe work 60.

The controller 600 controls winding operation of the fiber bundle 700around the work 60 by the FW apparatus 200. That is, the controller 600controls operation of the fiber unwinding unit 20, the fiber bundleguiding unit 30 and the winding unit 40. Specifically, the controller600 can control, for example, the tensile force applied by the cylinder231, move of the fiber feed section 320, and rotational speed of therotation device 400. As a result, the controller can control the tensileforce applied to the fiber wound around the work 60, the winding angleof the fiber relative to the work 60, the rotational speed of the work60, and the like. By this control, the fiber bundle 700 can be woundaround the surface of the work 60 by appropriately combining the hoopwinding, the high-angle helical winding, or the low-angle helicalwinding.

(A-3) Cracking in Second Hoop Layer

In the high-pressure tank 100 in the present embodiment, a crack mayoccur in the surface of the second hoop layer 76 that is an outmostlayer. Occurrence of the crack in the second hoop layer 76 is describedhereinafter.

FIGS. 6A to 6C are explanatory diagrams illustrating a process in whichthe crack occurs in the second hoop layer 76 and are partially enlargedschematic cross-sectional views of an outer wall of the high-pressuretank 100. FIG. 6A shows a state when the high-pressure tank 100 isfilled with hydrogen. If the high-pressure tank 100 is filled withhydrogen, the liner 10 expands. As a result, the entire outer wall ofthe high-pressure tank 100 including the liner 10 and the reinforcementlayer 70 curves toward the outside of the tank.

FIG. 6B shows a state when an amount of compressed hydrogen stored inthe high-pressure tank 100 has decreased compared with the state in FIG.6A. If the amount of the compressed hydrogen stored in the high-pressuretank 100 decreases, an expanding degree of the liner 10 decreases. As aresult, a curvature degree of the reinforcement layer 70 also decreasesalong with the liner 10. Since the second hoop layer 76 is the outmostlayer in the reinforcement layer 70, it is most vulnerable to shock orheat from the outside. Accordingly, the resin constituting the secondhoop layer 76, in particular, deteriorates faster than the other resinsin the reinforcement layer 70. If the deterioration of the resinconstituting the second hoop layer 76 progresses, the resin constitutingthe second hoop layer 76 becomes brittle, which reduces flexibility andtoughness of the second hoop layer 76. In such a case, if the amount ofthe compressed hydrogen stored in the high-pressure tank 100 decreases,the second hoop layer 76 cannot follow transformation of the otherlayers, and then the second hoop layer 76 and the second helical layer78 may separate from each other, as shown in FIG. 6B.

FIG. 6C shows a state when the amount of the compressed hydrogen storedin the high-pressure tank 100 has further decreased compared with thestate in FIG. 6B. When the resin constituting the second hoop layer 76deteriorates and the second hoop layer 76 peels off from the secondhelical layer 78, and the expanding degree of the liner 10 furtherdecreases, the second hoop layer 76 may buckle as shown in FIG. 6C. Ifthe second hoop layer 76 buckles, the crack is likely to occur at thebuckling portion in the second hoop layer 76. If the crack occurs in thesecond hoop layer 76, it becomes visible from the outside of thehigh-pressure tank 100. The crack may easily occur due to environmentdepending on the second resin used for the GFRP layer 72.

(A-4) Suppression of Cracking in Second Hoop Layer:

One of the reasons of cracking in the second hoop layer 76 is that thesecond hoop layer 76 peels off from the second helical layer 78, asdescribed above. There are multiple portions where the peeling of thesecond hoop layer 76 is likely to occur in the high-pressure tank 100.One of the portions where the peeling of the second hoop layer 76 islikely to occur, i.e., where resistance to the buckling is relativelylow, is a one-round portion including the final crossing portion 82disposed at the end of the winding of the glass fiber wound around inthe circumferential direction of the high-pressure tank 100 toconstitute the second hoop layer 76. This portion is also referred to asa terminal portion hereinafter. The tensile force of the winding fiberis easily released especially at the terminal portion of the glassfiber. As a result, the second hoop layer 76 is likely to peel off andthen, buckle or crack at the terminal portion.

In the present embodiment, as will be described below, the terminalportion of the glass fiber, where the second hoop layer 76 is likely topeel off, and another portion where the peeling of the second hoop layer76 is likely to occur are disposed so as not to overlap each other in astacking direction of the respective layers constituting thereinforcement layer 70 (hereinafter simply referred to as a stackingdirection). Accordingly, the portions where the second hoop layer 76 islikely to peel off are arranged so as not to overlap each other in thestacking direction, thereby suppressing the peeling of and the crack inthe second hoop layer 76.

The other portion where the second hoop layer 76 is likely to peel offis where a local stress is generated in the reinforcement layer 70. Theother portion can be also where deformation is relatively high. Thehigh-pressure tank 100 in the present embodiment has a stress-generatingportion where the local stress as described above is generated in thereinforcement layer 70. The stress-generating portion is at least one of(a) a convex portion locally forming a convex shape on the outer surfaceof the liner 10, (b) a step portion where the carbon fiber or the glassfiber cross itself at the transition part where the winding angle of thecarbon fiber or the glass fiber changes in the reinforcement layer 70,(c) a fiber joining portion where ends of the carbon fibers, ends of theglass fibers, or ends of the carbon fiber and the glass fiber are joinedtogether in the reinforcement layer 70, (d) an end crossing portionwhere the carbon fiber entwines and crosses the same carbon fiber or theglass fiber entwines and crosses the same glass fiber on at least one ofa winding start of the carbon fiber, a winding end of the carbon fiber,and a winding start of the glass fiber, and (e) a helical crossingportion where the carbon fiber crosses itself in the first helical layer71 disposed in contact with the liner 10.

FIG. 7 is a schematic cross-sectional view of an example of a positionalrelation between the terminal portion of the glass fiber 700 a and thestress-generating portion. FIG. 7 shows an enlarged partialcross-sectional view of the outer wall taken along the axis O of thehigh-pressure tank 100. In FIG. 7 , the one-round portion including thefinal crossing portion 82 of the glass fiber wound around in thecircumferential direction of the high-pressure tank 100 to constitutethe second hoop layer 76, i.e., the terminal portion, is shown as across section of the glass fiber 700 a. In FIG. 7 , thestress-generating portion is shown as the convex portion 14 locallyforming a convex shape on the outer surface of the liner 10. An areaoverlapping the convex portion 14 as the stress-generating portion inthe stacking direction of the reinforcement layer 70 is shown as a firstarea α. In the first area α, a local stress is generated by the convexportion 14, and thus the first area α corresponds to the “other portionwhere the second hoop layer 76 is likely to peel off”. An area exceptfor the first area α in the reinforcement layer 70 is shown as a secondarea β. FIG. 7 shows the terminal portion of the glass fiber disposed tooverlap the second area β in the stacking direction.

FIG. 8 is an explanatory diagram illustrating an example of the convexportion 14 formed on the outer surface of a liner 10. FIG. 8 is anenlarged schematic cross-sectional view of part of the outer wall of theliner 10 taken along the axis O of the high-pressure tank 100. FIG. 8shows a liner joining portion 15 joining a liner component 11 andanother liner component 12. When the liner components are joinedtogether, a convex structure is usually formed at the liner joiningportion 15 between the adjoining liner components. Although such aconvex structure can be cut off after joining the liner components, itneeds processing with extremely high precision to completely cut off theconvex structure, which may be difficult to adopt. If a cutting amountis too large, the liner 10 gets thin, which is not appropriate.Accordingly, as a result of the cutting to avoid the excessive cuttingamount, the convex portion 14 usually remains after the cutting theconvex structure. FIG. 8 shows a cutting line of the convex structure ina broken line and indicates that the convex portion 14 of height H isformed.

In the present embodiment, as shown in FIG. 7 , the terminal portion ofthe glass fiber is disposed so as not to overlap the convex portion 14in the stacking direction. Due to the formation of the convex portion 14on the outer surface of the liner 10, a local stress is generated in thefirst area α of the reinforcement layer 70. Accordingly, as thehigh-pressure tank 100 expands or contracts due to filling ordischarging of hydrogen, deforming degree of the reinforcement layer 70is likely to be larger at the portion where the stress is locallygenerated. As a result, the peeling or the buckling of the second hooplayer 76 is likely to occur. The terminal portion is disposed to overlapthe second area β in the stacking direction, thereby suppressing thepeeling of the second hoop layer 76 and the like.

FIG. 9 is an explanatory diagram illustrating another example of thestress-generating portion. FIG. 9 is a diagram illustrating an externalappearance of the work 60 in the middle of manufacturing thehigh-pressure tank 100.

FIG. 9 shows the first transition part 90 disposed in the CFRP layer 74.The first transition part 90 is where the low-angle helical layer 71 bchanges to the layer having a higher winding angle than that of thelow-angle helical layer 71 b, as described above. Although the carbonfiber is wound around at approximately constant winding angle in thefirst helical layer 71 and the first hoop layer 73 constituting the CFRPlayer 74, the winding angle drastically changes in the first transitionpart 90. In FIG. 9 , winding paths of the carbon fiber constituting thefirst transition part 90 are shown by winding paths 91 to 94. As shownin FIG. 9 , the carbon fiber is wound around by variously changing thewinding angle, and thus one or more crossing portions where the windingcarbon fiber crosses the same carbon fiber are created in the firsttransition part 90. Accordingly, the crossing portion of the carbonfiber causes a difference in level on the work 60. The crossing portionof the carbon fiber in the first transition part 90 is therefore shownas a step portion Cr1 in FIG. 9 . The step portion Cr1 generates a localstress in the reinforcement layer 70, and thus the step portion Cr1 inthe first transition part 90 could be the stress-generating portion likethe convex portion 14 of the liner 10 described above. The step portionCr1 in the first transition part 90 is also referred to as a first stepportion.

Similarly to the first transition part 90 shown in FIG. 9 , a stepportion similar to the first step portion is formed in the secondtransition part formed between the second helical layer 78 and thesecond hoop layer 76, described above, and it could be thestress-generating portion. Regarding the second transition part, terms“the low-angle helical layer 71 b”, “the layer having a higher windingangle than that of the low-angle helical layer 71 b”, and “the firsttransition part 90” in the foregoing description based on FIG. 9 may berespectively replaced with terms “the second helical layer 78”, “thesecond hoop layer 76”, and “the second transition part”. The stepportion Cr1 formed in the second transition part is also referred to asa second step portion.

FIG. 10 is an explanatory diagram illustrating another example of thestep portion as the stress-generating portion. When the high-pressuretank 100 is produced, the carbon fiber or the glass fiber, i.e., the towprepreg 710, for example, may be cut while being wound around the work60. Or, the tow prepregs 710 wound around the bobbins 201 to 204 may runout while being wound around the work 60. See FIG. 5 . In such cases, anew fiber is joined so as to continue to produce the high-pressure tank100. FIG. 10 is a schematic perspective view of the fiber joiningportion 80 formed by joining ends of the tow prepregs 710. The towprepregs 710 can be joined together by heat welding, for example. Thefiber joining portion 80 where the carbon fibers are joined together inthe CFRP layer 74 is also referred to as a first joining portion, whilethe fiber joining portion 80 where the glass fibers are joined togetherin the GFRP layer 72 is also referred to as a second joining portion.

According to the foregoing description, the fiber joining portion 80 inFIG. 10 is the fiber joining portion between the carbon fibers orbetween the glass fibers; however, it may be a different configuration.For example, it is possible to adopt a configuration in which, betweenthe CFRP layer 74 and the second helical layer 78 in the GFRP layer 72,a terminal end of the carbon fiber constituting the CFRP layer 74 and astating end of the glass fiber constituting the second helical layer 78are joined together. In such a case, the fiber joining portion 80 inFIG. 10 may be the portion where the terminal end of the carbon fiberand the starting end of the glass fiber are joined together. The portionwhere the terminal end of the carbon fiber and the starting end of theglass fiber are joined together is also referred to as a third joiningportion. These first joining portion, second joining portion and thethird joining portion cause a difference in level on the surface of thework 60. Therefore, each of the fiber joining portions described abovecould be the stress-generating portion like the convex portion 14 of theliner 10.

FIG. 11 is an explanatory diagram illustrating still another example ofthe stress-generating portion. FIG. 11 shows an external appearance ofthe work 60 in the middle of manufacturing the high-pressure tank 100.FIG. 11 shows a state in which, between the CFRP layer 74 and the secondhelical layer 78, the terminal end of the carbon fiber constituting theCFRP layer 74 and the stating end of the glass fiber constituting thesecond helical layer 78 are in Non-connected state. Specifically, FIG.11 shows a state in which an end crossing portion 86 is formed at awinding end of the carbon fiber and an end crossing portion 86 is formedat a winding start of the glass fiber on the surface of the CFRP layer74 that has been formed. The end crossing portion 86 is a portion wherethe carbon fiber 700 b entwines and crosses the same carbon fiber 700 bat a winding end of the CFRP layer 74. In addition, the end crossingportion 87 is a portion where the glass fiber 700 c entwines and crossesthe same glass fiber 700 c at the winding start of the second helicallayer 78.

The end crossing portion 86 or the end crossing portion 87 can beformed, for example, by winding the carbon fiber 700 b or the glassfiber 700 c around the work 60 once along its circumferential directionand then making the carbon fiber 700 b or the glass fiber 700 c entwineand cross the same carbon fiber 700 b or the same glass fiber 700 c.Alternatively, the end crossing portion 86 or the end crossing portion87 may be formed by making the carbon fiber 700 b or the glass fiber 700c entwine and cross the same carbon fiber 700 b or the same glass fiber700 c at a portion different from where the carbon fiber 700 b or theglass fiber 700 c is wound around once along the circumferentialdirection. If the tow prepregs are used as the carbon fiber 700 b andthe glass fiber 700 c, the end crossing portion 86 and the end crossingportion 87 can be secured to the work 60 by melting the resinsimpregnated into the tow prepregs by heating. The end crossing portion86 and the end crossing portion 87 cause a difference in level on thesurface of the work 60. Therefore, each of the end crossing portionsdescribed above could be the stress-generating portion like the convexportion 14 of the liner 10.

An end crossing portion similar to the end crossing portion 87 shown inFIG. 11 may be formed at an end of the winding start of the carbon fiberconstituting the CFRP layer 74 formed on the liner 10. Accordingly, theend crossing portion disposed at the starting end of the carbon fiberconstituting the CFRP layer 74 on the outer surface of the liner 10causes a difference in level on the outer surface of the liner 10, whichgenerates a local stress in the reinforcement layer 70. Therefore, suchan end crossing portion could be the stress-generating portion like theconvex portion 14 of the liner 10.

FIG. 12 is an explanatory diagram illustrating still another example ofthe stress-generating portion which is “the helical crossing portionwhere the carbon fiber crosses itself in the first helical layerdisposed in contact with the liner”. FIG. 12 is a perspective view ofthe external appearance of the work 60 in the middle of manufacturingthe high-pressure tank 100. In the present embodiment, as shown in FIG.2 , the low-angle helical layer 71 b is formed as the layer that isright above the liner 10 and in contact with the liner 10. The low-anglehelical layer 71 b that is formed as the layer right above the liner 10out of the low-angle helical layers 71 b is also referred to as aninmost low-angle helical layer 75. FIG. 12 shows a state in which theinmost low-angle helical layer 75 is formed on the liner 10. In theinmost low-angle helical layer 75, there is formed a helical crossingportion Cr2 where the carbon fiber wound by low-angle helical windingcrosses itself. In the inmost low-angle helical layer 75, the carbonfiber is wound around with a particular winding pattern showing aconstant winding angle. A helical crossing portion Cr2 is where thenumber of carbon fibers overlapping in the stacking direction is thelargest in the inmost low-angle helical layer 75.

The inmost low-angle helical layer 75 includes one or more helicalcrossing portions Cr2 and it usually includes a plurality of helicalcrossing portions Cr2 in accordance with a winding angle and a size ofthe liner 10. Since the carbon fiber is wound around at the constantwinding angle in the low-angle helical layer, a degree of the differencein level caused by the helical crossing portion Cr2 is lower than thatof the step portion Cr1 including the first step portion and the secondstep portion shown in FIG. 9 . However, rigidity of a materialconstituting the liner 10 such as a resin is usually higher than that ofthe resin included in the CFRP layer 74 and the GFRP layer 72. As aresult, the helical crossing portion Cr2 in the inmost low-angle helicallayer 75 formed right above the liner 10 locally generates larger stressin the reinforcement layer 70, unlike the portions where the carbonfiber or the glass fiber crosses itself in another low-angle helicallayer, i.e., the low-angle helical layer 71 b other than the low-angleinmost helical layer 75 and the second helical layer 78. Therefore, thehelical crossing portion Cr2 could be the stress-generating portion likethe convex portion 14 of the liner 10.

The layer that is right above the liner 10 and in contact with the liner10 may be the high-angle helical layer 71 a instead of the low-anglehelical layer 71 b. However, the degree of the difference in levelsformed on the surface of the helical layer due to the helical crossingportion is usually higher in the low-angle helical layer 71 b than inthe high-angle helical layer 71 a. Therefore, the stress generated inthe reinforcement layer 70 is larger in the case of disposing thelow-angle helical layer 71 b as the layer right above the liner 10 thanin the case of disposing the high-angle helical layer 71 a.

As described above, when the terminal portion of the glass fiber isdisposed to overlap the second area β in the stacking direction, alocation of the stress-generating portion needs to be specified andlocations of the first area α and the second area β defined by thelocation of the stress-generating portion need to be specified, forexample. When the stress-generating portion is the first step portion inthe CFRP layer 74 described as the step portion Cr1 in FIG. 9 or thehelical crossing portion Cr2 in the inmost low-angle helical layer 75shown in FIG. 12 , locations of the first step portion and the helicalcrossing portion Cr2 can be specified using first winding conditions inprocedures for forming the CFRP layer 74. The first winding conditionsinclude the rotational speed of the liner 10, the winding angle of thecarbon fiber with respect to the liner 10, and the tensile force appliedto the carbon fiber to be wound around the liner 10.

Furthermore, when the stress-generating portion is the second stepportion between the second helical layer 78 and the second hoop layer 76described as the step portion Cr1 in FIG. 9 , a location of the secondstep portion can be specified using second winding conditions at leastin procedures for forming the second helical layer 78 and procedures forforming the second transition part where the second helical layer 78changes to the second hoop layer 76. The second winding conditionsinclude the rotational speed of the liner 10, the winding angle of theglass fiber with respect to the liner 10, and the tensile force appliedto the glass fiber to be wound around the liner 10. As described above,the controller 600 controls the tensile force applied by the cylinder231, the conveyance by the fiber feed section 320, and the rotationalspeed of the rotation device 400 so as to control the tensile force ofthe fiber to be wound around the work 60, the winding angle of the fiberwith respect to the work 60, the rotational speed of the work 60, andthe like. Therefore, the location of each stress-generating portion canbe specified using a control history of the controller 600.

When the stress-generating portion is the convex portion 14 disposed onthe liner 10, as described above, the location of the stress-generatingportion needs to be specified in advance when the liner 10 is installedin the FW apparatus 200. When the stress-generating portion is the firstjoining portion joining the carbon fibers or the second joining portionjoining the glass fibers, as described above, a relative location of thestress-generating portion in the work 60 needs to be specified when thefibers are joined together. When the stress-generating portion is thethird joining portion joining the carbon fiber and the glass fiber, aportion of the winding end of the carbon fiber, or a portion of thewinding start of the glass fiber between the CFRP layer 74 and thesecond helical layer 78, as described above, a relative location of thefiber joining portion 80 in the work 60 needs to be specified when sucha stress-generating portion is formed.

According to the high-pressure tank 100 in the present embodiment,configured as described above, and the method for manufacturing thehigh-pressure tank 100, the one-round portion including the finalcrossing portion 82 at the end of the winding of the glass fiberconstituting the second hoop layer 76 is disposed to overlap the secondarea β, defined by at least one of the stress-generating portionsdescribed above, in the stacking direction. That is, the terminalportion where the crack is likely to occur in the surface of thereinforcement layer 70 and the stress-generating portion that generatesthe local stress in the reinforcement layer 70, which is likely to causethe crack in the surface of the reinforcement layer 70, are disposed soas not to overlap each other in the stacking direction. Therefore, evenif an increase and decrease cycle of an inner pressure is repeated forthe high-pressure tank 100, the crack in the surface of thereinforcement layer 70 can be reduced. That is, the peeling of thesecond hoop layer 76 at the terminal portion can be suppressed, and thebuckling and the cracking of the second hoop layer 76 resulted from thepeeling can be suppressed.

In the present embodiment, since pressure resistance is mainly securedby the CFRP layer 74 in the high-pressure tank 100, influence on a tankperformance is practically small if the crack occurs in the surface ofthe second hoop layer 76. However, if the crack occurs in the surface ofthe high-pressure tank 100, a user may be concerned about occurrence ofabnormality in the tank. Since the cracking in the second hoop layer 76is suppressed in the present embodiment, it is possible to reduce theuser's concern about the performance in relation to a change in anappearance of the tank that hardly affect the tank performance.

Additionally, the effect of suppressing the cracking in the second hooplayer 76 as described above can be particularly noticeable when thestress-generating portion is at least the second crossing portion in thesecond transition part where the second helical layer 78 changes to thesecond hoop layer 76. This is because the second crossing portion is astructure disposed between the second helical layer 78 and the secondhoop layer 76 where the peeling of the second hoop layer 76 occurs, andthus the influence on the peeling of the second hoop layer 76 isespecially large.

In the present embodiment, the tow prepregs are used as the carbon fiberfor forming the CFRP layer (strengthening layer) 74 and the glass fiberfor forming the GFRP layer (protective layer) 72. As a result, theeffect of suppressing the cracking in the second hoop layer 76 isparticularly noticeable. As a method for forming a fiber-reinforcedplastic layer like the CFRP layer 74 and the GFRP layer 72 by a filamentwinding method, a wet method is known in addition to a dry method usingthe tow prepreg as in this embodiment. In the wet method, a fiberpreliminarily impregnated with resin like the tow prepreg is notprepared. The resin is impregnated into the fiber by, for example,immersing the fiber in a resin tub storing melting resin right beforewinding the fiber around the work, and then the filament winding methodis performed. The dry method enables high-speed filament winding;however, an amount of the resin impregnated into the fiber wound aroundthe work is usually smaller, compared with the wet method. It isconsidered that as the amount of the resin impregnated into the fiber issmaller, the second hoop layer 76 is more likely to peel off when thehigh-pressure tank 100 expands and contracts. According to thisembodiment, even if the dry method, which is more likely to cause theproblem of peeling the second hoop layer 76, is adopted, the cracking inthe second hoop layer 76 can be suppressed. However, the wet method mayadopt the configuration in which the terminal portion of the glass fiberis disposed to overlap the second area β in the stacking direction.

In the present embodiment, the terminal portion of the glass fiber,where the second hoop layer 76 is likely to peel off, and thestress-generating portion that generates the local stress in thereinforcement layer 70, which is likely to cause the peeling of thesecond hoop layer 76, are disposed so as not to overlap in the stackingdirection. There may be several stress-generating portions in thehigh-pressure tank 100, as described above. In order to more effectivelyreduce the cracking in the surface of the reinforcement layer 70 in thehigh-pressure tank 100, the number of stress-generating portions notoverlapping the terminal portion in the stacking direction may belarger. Father, none of the stress-generating portions may overlap theterminal portion in the stacking direction.

In order to specify the positional relation between the terminal portionof the glass fiber and the stress-generating portions in thehigh-pressure tank, it is necessary to perform actions to observecross-sections taken by cutting the high-pressure tank in aperpendicular direction relative to the axis direction on the entirehigh-pressure tank at sufficiently short intervals, for example.Repeatedly observing the cross-sections of the high-pressure tank, asdescribed above, makes it possible to specify the locations of theterminal portion of the glass fiber and each of the stress-generatingportions, that is, the stress-generating portions generating the localstress in the reinforcement layer such as the convex portion formed onthe outer surface of the liner, the crossing portions of the carbonfiber or the glass fiber wound around the liner, and the joining portionjoining the carbon fibers or the glass fibers. Alternatively, thelocations of the crossing portions of the carbon fiber or the glassfiber wound around the liner and the joining portion may be specified bydry distilling the high-pressure tank so as to volatilize a resincomponent constituting the reinforcement layer and leave the fibers.

B. Second Embodiment

FIG. 13 is a perspective view of the high-pressure tank 100 in a secondembodiment of the present disclosure installed in a fuel cell vehiclefunctioning as a high-pressure tank mounting apparatus. Thehigh-pressure tank 100 according to the second embodiment has aconfiguration that is similar to that of the high-pressure tank 100according to the first embodiment. Thus, components that are the same asthose in the first embodiment are denoted with the same referencenumerals and will not be elaborated upon here.

The high-pressure tank 100 is secured to structural members 29 withfixing members 26. The structural members 29 are secured to a vehiclebody of the fuel cell vehicle that is not shown. As shown in FIG. 13 ,in the present embodiment, the fixing members 26 are formed in a beltshape, curved so as to follow the circumference of the high-pressuretank 100, and fastened to the structural members 29 by fasteningportions 28 disposed on both ends. Parts of the fixing members 26 thatare curved and contact with the surface of the high-pressure tank 100are also referred to as contact portions 27. The fixing members 26 needto be strong enough to secure the high-pressure tank 100 and can be madeof metal, for example. In the present embodiment, two fixing members 26are used; however, one or more than two fixing members 26 may be used.In addition, the fixing members 26 may be in a shape other than the beltshape. The fixing members 26 need to secure the high-pressure tank 100to the high-pressure tank mounting apparatus while making contact withthe outer surface of the high-pressure tank 100 at the contact portions27 and fastened to the structural members 29 by the fastening portions28.

In the present embodiment, at least part of the terminal portion of theglass fiber constituting the second hoop layer 76 on the outer surfaceof the high-pressure tank 100 is covered with any one of the contactportions 27 of the fixing members 26.

With such a configuration, the part of the terminal portion of the glassfiber covered with the contact portion 27 is pushed by the fixing member26 from the outside of the tank. Accordingly, at the part of theterminal portion of the glass fiber covered with the contact portion 27,the peeling of the second hoop layer 76 from the second helical layer 78and the buckling of the second hoop layer 76 are suppressed. As aresult, even if the increase and decrease cycle of the inner pressure isrepeated for the high-pressure tank 100, the effect for reducing thecrack in the surface of the reinforcement layer 70 can be enhanced.

C. Alternative Embodiments

(C1) The stress-generating portions are not limited to theconfigurations described in detail in the foregoing embodiments. Forexample, in the forgoing embodiments, as the convex portion formed onthe outer surface of the liner 10 as the stress-generating portion, theconvex portion 14 formed at the liner joining portion 15 is described;however, it may be a convex portion disposed at a different portion fromthe liner joining portion 15. Such a configuration can exhibit the sameeffect as that of the forgoing embodiments described above, if theterminal portion of the glass fiber constituting the second hoop layer76 is disposed to overlap the second area β in the stacking direction.

(C2) The high-pressure tank mounting apparatus is not limited to thefuel cell vehicle. It needs to be an apparatus equipped with a deviceconsuming the fluid filled in the high-pressure tank. The device is, forexample, a fuel cell if the fluid is hydrogen. If the high-pressure tankis secured to a structural member of a high-pressure tank mountingapparatus with the same kind of fixing member as that in the secondembodiment, the effect for suppressing the crack in the surface of thereinforcement layer 70 can be enhanced as in the second embodiment.

The present disclosure is not limited to the embodiments describedabove, and may be implemented in various ways without departing from thescope of the present disclosure. For example, the technical features ofany of the above embodiments corresponding to the technical features ofeach of the aspects described in Summary may be replaced or combinedappropriately, in order to solve part or all of the problems describedabove or in order to achieve part or all of the advantageous effectsdescribed above. Any of the technical features may be omittedappropriately unless the technical feature is described as essential inthe description hereof. For example, the present disclosure may beimplemented as the following aspects.

(1) According to one aspect of the present disclosure, a high-pressuretank is provided. The high-pressure tank comprises a liner including acylindrical portion and hemispherical dome portions on both sides of thecylindrical portion, and a reinforcement layer covering an outer surfaceof the liner. The reinforcement layer includes a strengthening layerthat is formed on the liner and includes a first helical layer includinga carbon fiber in helical winding and a first resin, and a first hooplayer including the carbon fiber in hoop winding and the first resin.The reinforcement layer includes a protective layer that is formed onthe strengthening layer and includes a second helical layer including aglass fiber in the helical winding and a second resin, and a second hooplayer formed on the second helical layer and including the glass fiberin hoop winding and the second resin. The high-pressure tank furthercomprises a stress-generating portion generating a local stress in thereinforcement layer. The stress-generating portion is at least one of(a) a convex portion locally forming a convex shape on the outer surfaceof the liner, (b) a step portion where the carbon fiber or the glassfiber crosses itself at a transition part where a winding angle of thecarbon fiber or the glass fiber changes in the reinforcement layer, (c)a fiber joining portion where ends of the carbon fibers, ends of theglass fibers, or ends of the carbon fiber and the glass fiber are joinedtogether in the reinforcement layer, (d) an end crossing portion wherethe carbon fiber entwines and crosses the same carbon fiber or the glassfiber entwines and crosses the same glass fiber on at least one of awinding start of the carbon fiber, a winding end of the carbon fiber,and a winding start of the glass fiber, (e) a helical crossing portionwhere the carbon fiber cross itself in the first helical layer disposedin contact with the liner. The reinforcement layer includes a first areathat overlaps the stress-generating portion in a stacking direction ofthe strengthening layer and the protective layer stacked one on theother and a second area that is an area except for the first area.One-round portion including a final crossing portion where the glassfiber entwines and crosses the same glass fiber at an end of winding ofthe glass fiber in the second hoop layer overlaps the second area in thestacking direction.

According to the high-pressure tank in this aspect, the one-roundportion including the final crossing portion where the crack is likelyto occur in the surface of the reinforcement layer and thestress-generating portion generating the local stress in thereinforcement layer, which is likely to cause the crack in the surfaceof the reinforcement layer, are disposed so as not to overlap each otherin the stacking direction. As a result, even if an increase and decreasecycle of an inner pressure is repeated for the high-pressure tank, thecrack in the surface of the reinforcement layer can be reduced.

(2) In the high-pressure tank in the forgoing aspect, the liner mayinclude a plurality of liner components and a liner joining portion maybe formed between adjoining liner components of the plurality of linercomponents. The high-pressure tank may include the convex portion formedon the outer surface of the liner as the stress-generating portion, andthe convex portion may be formed at the liner joining portion. Accordingto the high-pressure tank in this aspect, it is possible to suppresscracking in the surface of the reinforcement layer at the liner joiningportion, resulted from the stress generated in the reinforcement layerby the convex portion formed on the outer surface of the liner.

(3) In the high-pressure tank in the forgoing aspect, the first helicallayer may include a low-angle helical layer where a winding angle of thecarbon fiber with respect to an axis direction of the high-pressure tankis 0° or higher and 40° or lower. The step portion may be formed in thehigh-pressure tank as the stress-generating portion. The step portionmay include one or more first step portions where the carbon fibercrosses itself in a first transition part where the low-angle helicallayer changes to a layer having a higher winding angle than that of thelow-angle helical layer in the strengthening layer. According to thehigh-pressure tank in this aspect, it is possible to suppress crackingin the surface of the reinforcement layer, resulted from the stressgenerated in the reinforcement layer by the first step portion.

(4) In the high-pressure tank in the forgoing aspect, the step portionmay be formed as the stress-generating portion. The step portion mayinclude one or more second step portions where the glass fiber crossesitself in a second transition part where the second helical layerchanges to the second hoop layer. According to the high-pressure tank inthis aspect, it is possible to suppress cracking in the surface of thereinforcement layer, resulted from the stress generated in thereinforcement layer by the second step portion.

(5) In the high-pressure tank in the forgoing aspect, the fiber joiningportion may be formed as the stress-generating portion. The fiberjoining portion may include one or more first joining portions whereends of a plurality of the carbon fibers are joined together in thestrengthening layer. According to the high-pressure tank in this aspect,it is possible to suppress cracking in the surface of the reinforcementlayer, resulted from the stress generated in the reinforcement layer bythe first joining portion.

(6) In the high-pressure tank in the forgoing aspect, the fiber joiningportion may be formed as the stress-generating portion. The fiberjoining portion may include one or more second joining portions whereends of a plurality of the glass fibers are joined together in at leastone of the second helical layer and the second hoop layer. According tothe high-pressure tank in this aspect, it is possible to suppresscracking in the surface of the reinforcement layer, resulted from thestress generated in the reinforcement layer by the second joiningportion.

(7) In the high-pressure tank according to the forgoing aspect, a thirdjoining portion may be formed between the strengthening layer and thesecond helical layer. At the third joining portion, a terminal end ofthe carbon fiber constituting the strengthening layer and a starting endof the glass fiber constituting the second helical layer are joinedtogether. The high-pressure tank may include the fiber joining portionas the stress-generating portion, and the fiber joining portion mayinclude the third joining portion. According to the high-pressure tankin this aspect, it is possible to suppress cracking in the surface ofthe reinforcement layer, resulted from the stress generated in thereinforcement layer by the third joining portion.

(8) In the high-pressure tank according to the forgoing aspect, betweenthe strengthening layer and the second helical layer, the terminal endof the carbon fiber constituting the strengthening layer and thestarting end of the glass fiber constituting the second helical layermay be in Non-connected state. The end crossing portion may be formed inthe high-pressure tank as the stress-generating portion, and the endcrossing portion may be disposed on at least one of the terminal end ofthe carbon fiber and the starting end of the glass fiber. According tothe high-pressure tank in this aspect, it is possible to suppresscracking in the surface of the reinforcement layer, resulted from thestress generated in the reinforcement layer by at least one of theterminal end and the starting end.

(9) In the high-pressure tank in the forgoing aspect, the first helicallayer may include one or more low-angle helical layers where a windingangle of the carbon fiber with respect to an axis direction of thehigh-pressure tank is 0° or higher and 40° or lower. The helicalcrossing portion may be formed in the high-pressure tank as thestress-generating portion. The helical crossing portion may be where thecarbon fiber crosses itself in an inmost low-angle helical layerdisposed in contact with the liner of the low-angle helical layers, andwhere the number of the carbon fibers overlapping in the stackingdirection is the largest in the inmost low-angle helical layer.According to the high-pressure tank in this aspect, it is possible tosuppress cracking in the surface of the reinforcement layer, resultedfrom the stress generated in the reinforcement layer by the helicalcrossing portion in the inmost low-angle helical layer.

(10) According to another aspect of the present disclosure, provided isa high-pressure tank mounting apparatus for mounting the high-pressuretank according to any one of (1) to (9). This high-pressure tankmounting apparatus comprises a structural member to which thehigh-pressure tank is secured, and a fixing member including a contactportion and a fastening portion and securing the high-pressure tank tothe structural member while making contact with an outer surface of thehigh-pressure tank at the contact portion and being fastened to thestructural member at the fastening portion. At least part of theone-round portion including the final crossing portion of the glassfiber is covered with the contact portion of the fixing member on theouter surface of the high-pressure tank. According to the high-pressuretank mounting apparatus in this aspect, effect for reducing the crack inthe surface of the reinforcement layer in the high-pressure tank can beenhanced.

The present disclosure may be implemented in various aspects other thanthose described above. For example, it may be implemented in an aspectsuch as a method for manufacturing the high-pressure tank.

What is claimed is:
 1. A method for manufacturing a high-pressure tank,the method comprising: preparing a liner including a cylindrical portionand hemispherical dome portions on both sides of the cylindricalportion; forming a strengthening layer on the liner, the strengtheninglayer including a first helical layer including a resin-impregnatedcarbon fiber in helical winding and a first hoop layer including aresin-impregnated carbon fiber in hoop winding; forming a protectivelayer on the strengthening layer, the protective layer including asecond helical layer including a resin-impregnated glass fiber inhelical winding and a second hoop layer including a resin-impregnatedglass fiber in hoop winding to form an outer surface of thehigh-pressure tank; and upon winding the resin-impregnated glass fiberin a circumferential direction of the high-pressure tank to form thesecond hoop layer, disposing a one-round portion including a finalcrossing portion to overlap a second area in a stacking direction of areinforcement layer, the final crossing portion being a portion wherethe resin-impregnated glass fiber entwines and crosses the sameresin-impregnated glass fiber at an end of winding of theresin-impregnated glass fiber, the reinforcement layer including thestrengthening layer and the protective layer stacked one on the other,the second area being an area except for a first area in thereinforcement layer, wherein the first area is an area overlapping astress-generating portion in the stacking direction, thestress-generating portion generating a local stress in the reinforcementlayer, and the stress-generating portion is at least one of (a) a convexportion locally forming a convex shape on an outer surface of the liner,(b) a step portion where the resin-impregnated carbon fiber or theresin-impregnated glass fiber cross itself at a transition part where awinding angle of the resin-impregnated carbon fiber or theresin-impregnated glass fiber changes in the reinforcement layer, (c) afiber joining portion where ends of the resin-impregnated carbon fibers,ends of the resin-impregnated glass fibers, or ends of theresin-impregnated carbon fiber and the resin-impregnated glass fiber arejoined together in the reinforcement layer, (d) an end crossing portionwhere the resin-impregnated carbon fiber entwines and crosses the sameresin-impregnated carbon fiber or the resin-impregnated glass fiberentwines and crosses the same resin-impregnated glass fiber on at leastone of a winding start of the resin-impregnated carbon fiber, a windingend of the resin-impregnated carbon fiber, and a winding start of theresin-impregnated glass fiber, and (e) a helical crossing portion wherethe resin-impregnated carbon fiber crosses itself in the first helicallayer disposed in contact with the liner.
 2. The method formanufacturing the high-pressure tank according to claim 1, wherein towprepregs are used as the resin-impregnated carbon fiber and theresin-impregnated glass fiber.